1. Field of the Invention
The present invention relates to systems and methods for the translation and presentation of digital data, and in particular, to a method and apparatus for translating an input data packet from a first input format to a second format.
2. Description of the Related Art
Television programs are distributed to viewers by a variety of broadcasting methods. These methods include traditional analog broadcast television (National Television Systems Committee or xe2x80x9cNTSCxe2x80x9d standard), the upcoming digital broadcast television (Advanced Television Systems Committee or xe2x80x9cATSCxe2x80x9d standard), cable television (both analog and digital), satellite broadcasting (both analog and digital), as well as other methods. These methods allow channels of television content to be multiplexed and transmitted over a common transmission medium. Typically, the program material and supporting data such as program guides are transmitted as packetized data in a time-division multiple access (TDMA) channel scheme. Typically, the data packets containing program material are compressed to reduce their size.
High definition television (HDTV) improves substantially upon the image and audio quality of basic broadcast television. However, uncompressed HDTV signals include much more information (typically well over a gigabit per second). When transmitted, even highly compressed HDTV signals require significantly more bandwidth than standard video.
Since the advent of satellite-broadcast television, the advanced television systems committee (ATSC) prepared, and the Federal Communications Commission (FCC) adopted a standard protocol for terrestrial high definition broadcasts. This standard was based on protocols developed by the motion picture experts group (MPEG)xe2x80x94specifically, MPEG-2 video on MPEG-2 transport.
In the early market penetration phases of HDTV, the cost to transmit uncompressed HDTV via satellite or terrestrial fiber optic circuits are not justified by the relatively small audience. Standard definition television (SDTV) signals having a lower bandwidth and a higher audience are often distributed in a xe2x80x9ccontribution qualityxe2x80x9d, a quality higher than normal transmission permitting alteration of the signal by affiliates. HDTV, which is in an early stage of development, is typically distributed in a format fully compressed and ready for broadcast xe2x80x9cbroadcast qualityxe2x80x9d. These signals are reduced in bandwidth to less than 18.5 megabits per second in a format directly compatible and ready for ATSC broadcast.
Without translation, the satellite broadcasters would have to fully decode the ATSC signal into an uncompressed digital stream, then re-encode the stream into the proper format and protocol. Unfortunately, this solution is undesirable, for several reasons. First, the decode/recode process induces errors, resulting in degradation of the output signal. Second, to minimize the reduction in the quality of the recoded signal, the bit rate of the second encode cycle may be larger than the original coding rate, thus increasing bandwidth. The reduction in signal quality is worse than one might assume. One of the most difficult tasks for an MPEG encoder is to code an MPEG artifact. Consequently, if difficulties in the first encoding process result in artifacts, these artifacts will cause even greater difficulties in the next encoding process. Third, the decode/recode process requires relatively expensive decoder/encoder hardware. What is needed is a method and apparatus for translating input data packets from a first protocol to a second protocol, without losing signal quality or requiring additional bandwidth or hardware. The present invention satisfies that need.
To address the requirements described above, the present invention discloses a method, apparatus, and article of manufacture for translating an input data packet from an input format to at least one output data packet in an output format. The method comprises the steps of reading a series of data packets in the first format, the data packets including a data type identifier, wherein at least some of the data packets include first time synchronization data and at least some of the data packets include payload data; identifying data packets of interest in the series of data packets according to data type using the data type identifier; identifying data packets from the data packets of interest having time synchronization information; generating second time synchronization information from the first time synchronization information for the data packets having time synchronization information, and generating at least one output data packet in the output data format having the second time synchronization information. In one embodiment, the method further comprises the steps of identifying data packets from the data packets of interest having payload data, and assembling at least one output data packet in the second format having the payload data.
The apparatus comprises a receiver for accepting the series of data packets in the first format, the data packets including a data type identifier, wherein at least some of the data packets include first time synchronization data and at least some of the data packets include payload data; a translator, comprising a processor, communicatively coupled to the receiver, the processor for performing instructions; a memory, communicatively coupled to the processor, the memory storing instructions comprising a first instruction set to identify data packets of interest in the series of data packets according to the data type identifier, a second instruction set to identify data packets from the data packets of interest having time synchronization information, a third instruction set to generate second time synchronization information from the first time synchronization information for the data packets having first time synchronization information and a fourth instruction set to generate at least one output data packet in the second format having the second time synchronization information.